Glucose oxidase (β-D-glucose:oxygen 1-oxidoreductase; EC 1.1.2.3.4) catalyzes the oxidation of β-D-glucose to gluconic acid, by utilizing molecular oxygen as an electron acceptor with the simultaneous production of hydrogen peroxide. Microbial glucose oxidase is currently receiving much attention due to its diverse applications in the chemical, pharmaceutical, food, beverage, clinical chemistry, biotechnology and other industries. Novel applications of glucose oxidase in biosensors have increased demand in recent years. Glucose oxidases have been isolated from various microbial sources.
The Aspergillus niger enzyme glucose oxidase is used e.g. in the food processing and pharmaceutical industries, and as a component of immunoassays and biosensors in the medical diagnostics field. The enzyme is also used to manufacture miniature biofuel cells that can power biomedical implants such as biosensors and insulin pumps. The output of these devices is limited by the performance of glucose oxidase within the anodic compartment.
In particular, three enzyme properties are relevant in the context of biofuel cells: (1) the rate of electron transfer from the electrode to the enzyme (the intrinsic enzyme activity); (2) the activity of the enzyme under physiological conditions (pH 7.4 and 5 mM glucose); and (3) the thermal stability of the enzyme.
WO89/126675 describes the production of glucose oxidase from Aspergillus niger in recombinant systems and WO 2008/079227 A1 relates to a obtained from Aspergillus niger formulated in a composition conferring improved storage stability. Glucose oxidases from different origins have also been disclosed including marine algae, e.g. Chondrus crispus (U.S. Pat. No. 7,544,795, U.S. Pat. No. 6,924,366), filamentous fungi, e.g. Cladosporium spp. (WO 95/29996, WO 1998/020136, U.S. Pat. No. 5,834,280) and Talaromyces flavus (U.S. Pat. No. 6,054,318). WO2012/017008 A1 discloses variants of Aspergillus niger glucose oxidase with altered enzymatic efficiency compared to the wild-type glucose oxidase.
However, the availability of glucose oxidases with improved properties for numerousness applications would be highly advantageous.